In the uplink, the common radio resource shared among the user terminals is the total amount of tolerable interference, which is defined as the average interference over all the receiving (Rx) antennas. A relative measure of total interference is Rise over Thermal (RoT), i.e. total interference relative to thermal noise.
Uplink load control adjusts the load headroom for a cell so that the measured RoT is controlled towards a target RoT. The RoT measurement is available typically every radio frame (e.g., 10 ms). The uplink scheduler allocates available uplink (UL) load to scheduled UEs who require higher uplink bit-rate and reduce the granted uplink bit-rate of some scheduled UEs when the system is overloaded. Due to the large delay in uplink load control and uplink scheduler, including RoT measurement delay, Node B processing delay, grant processing delay, and the like, large RoT oscillation can occur, either higher or lower than the RoT target, and the RoT peak can last a long time before the RoT is reduced to an acceptable level. The reason for the peaks is typically a power rush in the UL, due to the coupling of the inner power control loops of the UEs.
The load factor represents a portion of uplink interference that a certain channel of a certain UE generates, and is defined as the interference due to the channel of that UE divided by the total interference. The total load factor of different channels equals to the sum of load factors due to the different channels.
Uplink load estimation estimates the load that has been or will be generated in each cell from different channels. Power based load estimation means load estimation according to the original definition of load factor as described above. A remarkable benefit of power based load estimation is that it is receiver independent and can naturally capture the receiver gain of various types of receivers.
UE selects enhanced transmission format combination (E-TFC) based on the constraints given by the maximum allowed transmission (Tx) power, the available data in the UE Tx buffer, and the scheduling grant sent by the Node Bs.                The available data in the UE Tx buffer determines the maximum data rate and the E-TFC (E-TFCdata) with which the UE needs to transmit.        The maximum allowed Tx power dividing downlink physical control channel (DPCCH) Tx power determines the maximum power offset with which the UE can transmit due to the Tx power limitation, which can in turn be mapped to an E-TFC limitation (E-TFC power).        The scheduling grant can directly be mapped to an E-TFC limitation given by the scheduler (E-TFCgrant).        
The UE then selects the lowest allowed E-TFC (the minimum one among E-TFCdata, E-TFCpower, and E-TFCgrant) to transmit data.
In order to reduce the RoT peak level and suppress RoT peaks quickly, Fast Congestion Control (FCC) scheme has been introduced in Reference [1] and Reference [2]. It is proposed that transmission power control (TPC) down commands are sent to targetable UEs when measured RoT exceeds a target level. As FCC reacts much faster than uplink load control and scheduler, RoT can be better controlled and uplink load can be more efficiently utilized.
However, the RoT measurement used to trigger FCC should be updated at least as fast as the execution of inner loop power control, i.e. updated every slot (e.g., 0.667 ms). This increases complexity and requires more capable hardware.
Another drawback of FCC is that block error rate (BLER) of the targeted UEs by FCC will substantially increase. This may cause problem especially for UEs with relatively high QoS requirements. In this regard, the FCC scheme cannot be utilized too aggressively, and some load margin still needs to be reserved,